SB 608 
.C6 F2 
Copy 1 

Issued February 9, 191' 

PORTO RICO AGRICULTURAL EXPERIMENT STATION, 

D. "W. MAY, Special Agent in Charge, 

Mayaguej!, P. R. 



Bulletin No. 17. 



FUNGUS DISEASES OF COFFEE IN 
PORTO MCO. 



G. L. FAWCETT, 

Plant Pathologist. 



UNDER THE SUPERVISION OF 

OTTICE OF EXPERIMENT STATIONS, 

U. S. DEPARTMENT OF AGRICULTURE. 



WASHINGTON: 
GOVERNMENT PRINTING OFFICE. 



^^oaogHfk 



Issued February 9, 1915. 

PORTO RICO AGRICULTURAL EXPERIMENT STATION, 

D. "W. MAY, Special Agent in Charge, 

Mayaguez, P. R, 



Bulletin No. 17. 



EUNaUS DISEASES OF COFFEE IN 
PORTO RICO. 



G. L. FAWCETT, 

Plant Pathologist. 



UNDEB THE SXJPERVISION OF 

OmCE or EXPERIMENT STATIONS, 

U. S. DEPAETMENT OF AQEICtTLTXTRE. 



WASHINGTON: 
GOVERNMENT PRINTING OmOE. 



Cfi 



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PORTO EICO AGRIOTTLTUEAL EXPERIMENT STATION. 

[Under the supervision of A. C. True, Director of the Office of Experiment Stations, 
United States Department of Agriculture.] 

Walter H. Evans, GMef of Division of Insular SaUons, Office of Experiment 

Stations. 

STATION STAFF. 

D. W. Mat, Special Agent in Charge. 

P. L. GiLE, Chemist. 

G. L. Fawcett, Plcmt Pathologist. 

C. F. KiNMAN, Horticulturist. 

R. H. Van Zwaluwenbubg, Entomologist. 

T. B. McClelland, Assistant Horticulturist. 

J. O. Carrero, Assistant Chemist. 

W. E. Hess, Expert Gardener. 

C. Alemab, Jr., Clerk. 

(2) 



FEB 26 1915 



MM.i i iiWfgwgi. iJ &js>fejWteffittaa a iiflig^ 



*5^ 



LETTER OF TRANSMITTAL. 



Porto Rico Agricultural Experiment Station, 

Mayaguez, P. R.^ October 15, 1911^. 
Sir: I transmit herewith a manuscript on Fungus Diseases of 
Ck)ffee in Porto Eico. 

The seriousness of these troubles from the standpoint of one of the 
leading industries of Porto Rico justify the studies herein set forth, 
and the methods suggested for combating the diseases, which are 
now causing enormous losses, should be widely disseminated among 
the planters of the island. 

I respectfully recommend that this manuscript be issued as Bul- 
letin No. 17 of this station and that it be published in both English 
and Spanish. 

Respectfully, D. W. May, 

Special Agent in Charge. 
Dr. A. C. True, 

Director Office of Experiment Stations, 

U. S. Department of Agriculture, Washington, D, C. 

Recommended for publication. 
A. C. True, Director. 

Publication authorized. 
D. F. Houston, 

Secretary of Agriculture. 
(3) 



CONTENTS, 



Page. 

Introduction 7 

Leaf rot or thread blight (Pellicularia koleroga) 8 

Leaf spot {Stilbella fiavida) 11 

Root diseases 15 

Berry spot (Cercospora coffeicola) 21 

Studies of the spot fungus 26 

Miscellaneous diseases 27 

Summary 29 

(5) 



ILLUSTRATIONS, 



Plate I. Coffee branch attacked by thread blight {Pellicularia koleroga), show- 
ing characteristic suspension of leaves by threads of the fungus 8 

II. Coffee leaves attacked by the leaf spot fungus {Stilhella flavida) 8 

III. Fig. 1. — Coffee tree attacked by the root disease fungus {Rosellinia sp.) 

Fig. 2. — Imperfect form of root disease fungus {Dematophora sp.) on 
Petiveria plants 16 

IV. Coffee leaves attacked by the zonal leaf spot {Cephalosporium sp.), 

showing upper and lower surfaces 16 

V. Trunk of coffee tree with Fusarium disease produced by inoculation. . 24 
VI. Root of coffee tree. Roughened bark due to nematodes. Roots 

killed by "white " root fungus 24 

VII. A. — Spot on leaf showir^ fruiting bodies of Stilhella flavida. B. — En- 
larged head of fruiting body of Stilhella flavida. C and D . — ^Threads 

of Pellicularia koleroga, showing brandling 24 

VIII. A. — Ascus and spores of Rosellinia sp. B. — Hyphse and spores of 

Dematophorasp. C. — Hyphse and spores of Cephalosporium s^ .. . 24 
(6) 



FUNGUS DISEASES OF COFFEE IN PORTO RICO. 



INTRODUCTION. 

Fungus diseases of coffee are common in Porto Rico, and in 
many instances destructive. The reduction in the yield and con- 
sequent loss which result from their activity are not definitely 
known, but they must be large. The small crop of many plan- 
tations is no doubt due to the constant though often inconspicuous 
defoliation and killing of the trees which they cause. It is desired 
not only to attract attention to these diseases, but to suggest such 
means of getting rid of them as have been shown by experience to be 
of value. The excellent but costly methods of fighting disease, such 
as those practiced in the case of the intensively cultivated citrus 
fruits, are not to be recommended so unhesitatingly for coffee, the 
profits from which are not so great as to make the cost of production 
of small importance. Moreover, coffee is often grown in extended 
plantings in mountainous country where it receives so little cultiva- 
tion as to be hardly more than a wild plant. Wliere these conditions 
exist it is not likely that any more attention will be given the diseases 
than in the past. But there are other, usually smaller, plantations 
where it would seem worth while to take advantage of any measures 
of value in keeping up their present good condition, either by fight- 
ing those diseases that have already become established or keeping 
them from the healthy young plantings. 

It is expected also that a publication of this nature will be of value 
in dispelling the idea entertained by some planters that the diseases 
of this plant have been so neglected as to be practically unknown, but 
only await scientific study to be entirely done away with. Some of 
the coffee diseases of Porto Rico are common to other coffee-growing 
countries, and were first described many years ago. Suggestions as 
to their control have been made from time to time by laboratory 
workers, but apparently the methods have never been tried by grow- 
ers, else such value as these suggestions possess would have been pre- 
viously realized. The knowledge of the life history of the parasitic 
organisms causing the diseases has led to no entirely successful 
method for their control, if this is taken to mean some way in which 
the diseases may be ver}^ easily eradicated without some expense and 
careful attention in application. 

(7) 



8 

LEAF EOT OR THREAD BLIGHT (Pellicularia koleroga)} 

This is quite common in all plantations except those at higher alti- 
tudes. Of all the coffee diseases it is perhaps the most conspicuous, 
its presence being usually indicated by the blackened leaves which, 
after having been attacked by the fungus, are held suspended for 
some time by its threads (PL I). It has been reported from various 
places in India and the East Indies and recently from Surinam, and 
no doubt is found throughout the coffee-growing regions of the West 
Indies. A disease similar in character has also been reported from 
Venezuela, where it is known as " candelillo " ; the real leaf rot which 
has been reported from that country is also known by that name. 

On examination, the threads of the fungus which cause the disease 
will be found on the lower side of the twigs where at each pair of 
leaves it branches to form a thin web covering their undersurfaces. 
On the newly attacked leaves this web is white, but later it becomes 
brown. The leaves on which the fungus has obtained a better foot- 
hold and which have turned black often have a finely mottled ap- 
pearance, due to the thickening of the web at the points where it is 
attached to the leaf. A fvirther stage is represented by the develop- 
ment of the web into a parchment-like membrane completely con- 
cealing the lower side of the leaf. This may be removed with a 
needle or knife point " like a piece of gold beater's skin." The webs 
correspond to the feeding form of the fungus, serving to absorb food 
material from the leaves ; the threads to the " traveling " form, by 
the extension of which along the stems and branches in the course of* 
growth it reaches fresh material on which to feed. The threads 
which are at first white become brown after a time, break and fall 
away, but fragments often remain, sometimes concealed by the bark, 
which serve as new sources of infection. When examined micro- 
scopically^ the dense places are seen to be made up of flattened, much 
branched threads, which besides acting as holdfasts may also serve 
to draw food material from the leaf, although the thread's which 
penetrate the leaf soon after it is attacked are probably more impor- 
tant in food absorption. No spores or reproductive bodies have been 
found in the Porto Eican fungus. The vegetative hyphae of the 
webs are much branched and interlaced, the branching being often 
at right angles. (PL VII, C.) 

The fungus avoids the sunlight, never growing on those parts of the 
tree which are exposed to the direct rays. Possibly this habit enables 
it to live on and injure trees from which the shade has been removed. 
It must have a moist atmosphere for active growth. During the 
drier months it remains quiescent, the affected leaves drop off, and the 
plantation may appear quite free from the disease, but enough of the 

1 See also U. S. Dept. Agr., Jour. Agr. Research, 2 (1914), No. 3, p. 231. 



Bui. 17, Porto Rico Agr. Expt. Station. 



Plate I. 




Coffee Branch Attacked by Thread Blight (Pellicularia koleroga), Showing 
Characteristic Suspension of Leaves by Threads of the Fungus. 



Bui. 17, Porto Rico Agr. Expt. Station. 



Plate II. 




Coffee Leaves Attacked by the Leaf Spot Fungus (Stilbella flavida). 



fungus remains to serve to reinfect the trees when the rains become 
frequent. Apparently it is favored by high temperatures, as it is 
less common in the cooler higher elevations where more favorable 
conditions prevail as to moisture than in the warmer though some- 
what drier low lands. It spreads from one part of the tree to another 
by growth, and in the same way to other plants and coffee trees in 
contact with the diseased coffee trees. To other trees, however, some 
distance away it is usually communicated by the fungus-infested 
leaves dropping or being carried by the wind and adhering to any 
moist leaf or stem on which they happen to fall, the fungus then 
sending out threads which securely glue the leaves to their new host. 
Each such leaf serves as a center of infection. That the diseased 
leaA'^es can not adhere so well to dried surfaces is one reason for the 
disease not spreading in dry weather. There is apparently no other 
way in which this fungus is distributed, and for this reason it would 
seem to be greatly handicapped in comparison with some spore-bear- 
ing fungi. It is, however, so widely distributed and has such a way 
of appearing suddenly in unexpected places that it would seem as 
though it possessed some other more effective though unapparent 
means of distribution. 

Besides coffee, the author has found this fungus on sour orange, 
the wild vines Luff a cegyptica and Cucumis anguria, and the culti- 
vated ornamentals Hibiscus and Croton. It is probably able to at- 
tack these plants only under very favorable conditions, as they usu- 
ally remain free from the disease even when surrounded by infested 
coffee trees. The fungus also attacks the coffee berries, about one- 
third of which are found to haA^e blackened grains, the large propor- 
tion of such grains indicating that some of the injury is due to 
Pellicularia. In any event the number of berries attacked is so small 
that as a berry disease it is of little importance. The loss occasioned 
by this disease is that which results from the destruction of green 
leaf tissue, and through this the lessened yield of berries. It is prin- 
cipally a leaf parasite, but also causes the death of young branches, 
which often die after defoliation. When the branch is not killed it 
can not again bear leaves until new growth has been made. The 
tree must be weakened and the yield correspondingly reduced by 
the loss of foliage. What the loss from this source may be it is im- 
possible to know, but if proportionate to the percentage of leaves 
killed it would equal more than one-fourth in some trees noticed. 
The loss of leaves is ordinarily much less and frequently many trees 
escape infection. The loss in yield of berries from this source in most 
plantations is not large. It has never been observed to kill the trees. 
Like the " mancha de hierro," it is rarely found on poor, half -starved 
trees for the reason, no doubt, that such trees usually are in rather 
dry situations and have less foliage. 
71478°— 15 2 



10 

Various remedies have been tried. The gathering and burning 
of the diseased leaves sometimes recommended gave poor results. 
Enough of the fungus remains on the stems to serve to reinfect the 
plant so that it is soon as badly diseased as before. The lime-sulphur 
sprays, of which both the boiled and unboiled were used, were in- 
effective, as was also the sulphur alone applied as powder. Bordeaux 
mixture is really effective.^ The fungus can not grow on a leaf 
covered with this spray, and it adheres better tlmn the other fungi- 
cides, especially when made up with twice the usual amount of lime. 
Owing to the frequent and heavy rains of the wet season even this 
spray is washed off to some extent after a few days. In attempting 
to increase the adhesion various substances were added to the mix- 
ture, including borax, but the ordinary mixture with merely an extra 
amount of lime was found to be better than any of these. In the 
use of any spray material difficulties are met with, among which is 
that of training the peon to direct the spray so as to cover the lower 
sides of the leaves and to be thorough in the work, leaving no un- 
sprayed, diseased leaves to serve as centers of infection. On many 
of the trees reinfection takes place from the pieces of fungus threads 
Avhich the spray has missed or which have been partly concealed 
under the bark, making necessary repeated sprayings if the trees are 
to be kept clean. It is possible to destroy the fungus entirely on 
some trees by one spraying and to prevent the infection of healthy 
trees to a large extent, but to exterminate the disease even with re- 
peated sprayings is difficult. The work of one year seemed to indi- 
cate that spraying furnished excellent means of checking the dis- 
ease, but further work has shown it to be less satisfactory than it first 
appeared. To open up the trees to the wind and air by felling the 
shade could only have a bad effect on the coffee and is not to be 
recommended. 

As. the nearest approach to a good way of controlling the disease 
Bordeaux mixture made up with 4 pounds of copper sulphate and 
8 pounds of unslaked lime or 16 pounds of air-slaked lime to 50 
gallons of water applied as spray to the underside of the leaves is 
recommended. In no event should a larger area be treated than can 
be conveniently looked over from time to time in order to note any 

1 In case Bordeaux mixture is to bo used in any except very small quantities it will 
be well to make up stock solutions of the required ingredients, and take from these from 
time to time as needed. In this way it will be always possible to have a freshly made 
up and effective solution, that having been made up for some time spoiling. The 
ordinary mixture, 4 : 4 : 50 formula, is made by dissolving 8 pounds of the copper 
sulphate in 25 gallons of water. The lime and water for the other stock solution is 
made by slaking 8 pounds of live lime, using enough water to form a thin paste and 
adding to 25 gallons of water. The Bordeaux mixture is made by taking one part of 
each of the stock solutions, two parts of water, and agitating the mixture thoroughly. It 
is often convenient to make the mixture in the spray pump. The formula used in the 
work with coffee differs from the above in having twice the amount of lime, which has 
the effect of making it adhere somewhat better to the foliage. 



11 

reappearance of the disease and resprayed when found necessary. 
Picking the leaves before the spraying will probably be of some 
assistance if care is taken to remove as carefully as possible all the 
threads on the twigs, using for the purpose the cheaper labor some- 
times available for picking the berries. 

LEAF SPOT {SUlieUa flavida). 

This disease does not seem to be known in Porto Eico by any 
definite common name, being merely referred to as a spotting of the 
leaves. In Venezuela and apparently elsewhere on the continent 
and Central America it is called " mancha de hierro," but no doubt 
this term is made to include other small spots of both fungus and 
insect origin. It is quite generally distributed throughout the coffee- 
growing region of America, having been reported from Mexico, the 
Antilles, and Brazil. In Porto Rico it is found principally in the 
higher altitudes, where it is favored by excessive rainfall. Lower 
down it is found near streams and where it is sheltered from winds 
and afforded a moist atmosphere during part of the year. It is more 
dependent on moisture than other coffee fungi, being unable to infect 
new leaves or to form new fruits except under conditions of extreme 
humidity. 

The disease is characterized by the occurrence on the leaves of 
small spots usually circular in outline, but sometimes ovoid along 
the veins. (PL II.) The newer ones are very dark, the older ones 
light colored. The spots are usually about 6 millimeters in diame- 
ter, although many of the older ones become 12 to 13 millimeters in 
diameter. Sometimes they fuse or give entrance to other tissue- 
destroying fungi which infect the intervening tissue, producing spots 
of considerable size. The worst affected leaves have from 30 to 40 
or even more spots, so that a large proportion of the leaf tissue is 
destroyed. On the upper surface of many of the spots and also to 
some extent on the lower surface may be seen hair-like projections 
from 1 to 1: millimeters long of a yellowish color, each bearing at the 
end a head so that they resemble minute pins. This is the reproduc- 
tive or fruiting stage of the fungus. (PI. VII, A and B.) Each 
spot produces a continuous crop of these hairs so long as weather 
conditions are favorable. The total number at any time is small 
and in an entire season but from 20 to 50 are produced in each spot, 
judging from the number of old filament bases. The largest number 
observed was 70 in a spot of 7 millimeters diameter. As the leaf 
spots become older, growth having stopped for any reason, such as 
the advent of the dry season, the diseased tissue falls away, leaving 
numerous circular openings in the leaf. In other leaf diseases the 
dead tissue remains. 



12 

Sometimes the fungus attacks young stems, where it causes con- 
spicuous scars and so weakens the points affected that they are easily 
broken by the wind. The berries also are attacked, a slight discolo- 
ration of the grain being frequently caused. 

The microscope shoAvs the filaments, which are solid, not hollow, as 
sometimes stated, to be made up of the fine fungus threads which 
are somewhat branched in the upper part to form the head. The 
ends of the threads are swollen and have sometimes been mis- 
taken for spores when seen in cross section (PL VII, B), and de- 
scribed as such. No real spores have ever been found in any of the 
numerous specimens examined. The fungus is distributed by the 
heads at the ends of the filaments being caught by the wind or rain- 
drops and carried to near-by leaves, a process facilitated by the heads 
becoming loosened in the older filaments through the formation of 
cavities or "lacunae" near the point of attachment. (PL VII, B.) 
The head is soon fastened to the leaf on which it happens to fall by 
the numerous threads which it sends out at the point of contact. 
Within less than a week a dark circular spot is formed and new fila- 
ments appear and new loosely attached heads are formed on these by 
means of which the spread of the disease is continued. Apparently 
this fungus has no other way of propagating itself, and the writer 
has not found any other stage of Stilbella fiavida, all inoculations 
into coffee with suspected forms resulting negatively. Among other 
fungi used in such inoculations was one which answers so fully to 
the descriptions of SphcBrostilbe flavida'^ that it may be consid- 
ered identical with that fungus. As Sfhcerostilbe fiavida is some- 
times referred to as the perfect stage of Stilbella favlda^ as full use 
as possible was made of the small amount of material available . This 
fungus was first found here on a berry, which, with others bearing 
Stilbella spots, had been sterilized externally and placed in a moist 
chamber. Later the same fungus was found on a coffee berry still 
attached to the tree, where several of the Nectria-like fruits had de- 
veloped in a spot made by Stilbella. These were studied more fully. 
Direct inoculations of the perithecia into coffee berries did not take. 
In drop cultures of the ascospores a Cephalosporium developed. In 
pure cultures from single ascospores this fungus and later a Fusa- 
rium developed. This material w^as used in inoculation both into 
the berries on the tree and into very thoroughly disinfected and 
washed berries in flasks. A slight infection resulted on the unpicked 
berries. On those in the flasks perithecia identical with those from 
which the ascospores had been taken developed. But in no case did 
Stilbella fiavida result from the inoculations. Those made into 
leaves did not take. The work failed to show any relation between 
the fungus used in the inoculations and Stilbella fiavida. Of the 

1 Massee, Roy. Bot. Gard. Kew, Bui. Misc. Inform., 1909, No, 8, pp. 337-341. 



13 

large number of berries affected with Stilbella examined no others with 
Sphaerostilbe were found, so that even if it were a stage of Stilbella 
it could play a very small role in the distribution of the disease in 
this island. If the fungus is a Basidiomycete, as assumed with some 
reason by Spegazzini/ it was not found to possess such a stage. 

It is of interest to note that, although the coffee plant is the princi- 
pal host of this fungus, numerous other plants are also affected to 
some extent. The writer has found it on such unrelated host plants 
as the orange, mango, Begonia, various ferns, several of the coitres 
{Commelina spp.), and guava {Inga vera), and bejuco de carro 
{Velia sicyoides), and have noticed the spots, but not fruits, on the 
yautia, banana, and also on several wild plants. The coitres, which 
are perhaps most affected, and the ferns and other plants of low habit 
of growth form in many places a continuous ground covering and 
catch the greater part of the falling propagative bodies which escape 
the coffee leaves, and are hence peculiarly subject to the disease. 
They are apparently able to communicate it to unaffected plants of 
the same kind and doubtless also to healthy coffee plants. There were 
noticed places where the coffee was not attacked until several weeks 
after the ground plants had become infected. 

When first taking up the study of coffee diseases in Porto Rico 
the " mancha de hierro " appeared of small importance, for the reason 
that the area affected is so restricted by climatic conditions. But the 
regions of the island most affected produce the best coffee, and if it 
were not for this disease they would give larger yields. The injury 
to the trees is not so much in the actual amount of the leaf tissue 
destroyed, although this may amount to one-fifth or even more of the 
entire amount^in the worst cases, but in the defoliations which take 
place after a time. The diseased leaves drop sooner than those not 
affected, and owing to the weakened condition of the tree are not soon 
replaced. After the first severe attack the base of each tree may be 
seen to be surrounded by a pile of green leaves several inches deep. 
The disease never kills the trees. They live on with scanty foliage 
and are able to put forth some new growth and bear a small amount 
of berries each year. 

The decrease in yield following an attack of the leaf spot is marked. 
In one experimental plat, where a record of the yield had been kept 
for some years, it was found to be 75 per cent. In this case the dif- 
ference between the trees before and after the attack was such as 
accompanies the loss of the greater part of the foliage. 

The fungus, Stilbella, also attacks the berries. As mentioned 
above, however, it does not do very much harm to the fruit — much 
less, in fact than that caused by the Cercospora fruit spot — for it 

iRev. Facult. Agron. y Vet, La Plata, 2 (1896), No. 22, p. 339. 



14 

never causes the fleshy part of the berry to adhere to the parchment, 
in this way making the pulping more difficult. Out of several lots of 
berries examined, of which all were affected by Stilbella, a varying 
nimiber, from 6 to 18 per cent, were so badly affected that the dis- 
coloration could not be removed in the process of polishing to which 
coffee is subjected in preparation for the market. 

An experiment in the control of this disease, was begun at the sub- 
station, La Carmelita, to test the efficiency of gathering and destroy- 
ing the diseased leaves, a method recommended in some publications 
on this subject. Ten trees in one of the worst diseased areas were 
selected for this purpose and the leaves with Stilbella spots removed, 
two rows of the surrounding trees being similarly treated to prevent 
too immediate reinfection from other trees. The effect of the leaf 
picking on the prevalence of the fungus was roughly determined by 
finding the relative proportions of diseased and healthy berries, both 
being counted, in the trees of the plat and in an equal number of 
those outside. The proportion of diseased berries in the trees of the 
plat in the crop immediately following the first picking of leaves 
was 38 per cent; in the outside trees, 10 per cent. During the year 
the leaves were picked at intervals of three months. At the end of 
the year the percentage of diseased berries in the trees with picked 
leaves had declined to 16 per cent, but in the outside trees had in- 
creased to 32 per cent. It is probable that an equally large increase 
of Stilbella-affected berries would have been found in the trees from, 
which the diseased leaves were picked if it had not been for this 
treatment, the disease having made great headway in all parts of 
the plantation. 

Further work in combating the disease was made impossible by 
a change in the management of the plantation where the work was 
being carried on. However, such results as have been obtained 
would indicate that the disease might be successfully combated by 
removing the diseased leaves. No doubt the defoliation so produced 
is as bad for the tree as that caused by the fungus, but if the work 
were carefully done the newly formed leaves would remain free 
from infection, except as they might be gradually reached from trees 
outside the treated area. The fact that the disease spreads com- 
paratively slowly and that the diseased leaves are readily recog- 
nized make this treatment more easily carried out. It would seem 
that this slow and apparently impracticable method might be really 
of value in combating the disease where the cheaper labor used on 
some of the plantations is available. 

Spraying with Bordeaux mixture will exterminate the fungus 
if weather conditions happen to be favorable, but it is almost useless 
where the disease is most prevalent because of the frequent rains. 
The fungus can not infect leaves that are not moist much of the 



15 

time; and when the leaves are dry, the time that Bordeaux would 
be most effective by adhering best, the disease is at a standstill, as 
any of the heads which happen to fall on such leaves do not germi- 
nate even if the}^ adhere. The violent downpours soon wash the 
fungicide from the smooth upper surfaces of the leaves, where it 
must adhere to be of any effe'Ct. Moreover, the hillsides are so steep 
in many places that only knapsack sprayers could be used, and these 
only with difficulty. In case spraying is resorted to, it will be of 
most value when applied to the healthy trees near the diseased 
ones or to those less severely attacked, for the reason that the spray 
will prevent the infection of the leaves to which it adheres, though 
having no effect in preventing the formation of new propagative 
bodies on the already existing spots. 

The disease does not spread with great rapidity. In one case 
observed it progressed about 200 yards in one year. Many plantings, 
probably newer ones, iire free from this pest, although climatic con- 
ditions are such that it could do much damage if once it obtained 
foothold. After it appears in such places it is merely a matter of 
time until the entire field is affected, and it is under these condi- 
tions, when only a small area is affected, that it can be combated to 
most advantage. Unless prevented, it will extend down the mountain 
slopes until it reaches drier conditions, the only obstacles to its prog- 
ress in other directions being strips of forest or grass land or an 
especially exposed or unshaded slope. The coffee of the " altura " 
requires less shade than that of the lower lands, but even there it is 
seldom that there is an excess of shade. If such exists, it could be 
lessened to advantage, for anj^thing making for drier conditions is 
unfavorable to this fungus. To cut the shade away entirely, how- 
ever, would be a remedy worse than the disease, and one which no 
experienced grower would try. 

ROOT DISEASES. 

In many plantations there are to be found places where all the 
coffee trees have died out, the largest of such treeless areas covering 
an acre or more. These areas are usually well marked, being sur- 
rounded by healthy trees. The death of the trees is due to the action 
of certain soil fungi which attack the roots, usually the upper ones, 
and the base of the trunk. The first indication that a tree has been 
attacked is the drooping and yellowing of the leaves, which later fall, 
beginning with those of the lower branches. The roots of the trees 
will be found to be well covered by the thread-like growth of the fungi 
and partly decayed. There are two types of the disease, which may 
be classified for convenience according to the color of the accompany- 
ing fungi as the black {Rosellinia sp.)' and white root diseases. The 

1 Apparently RoseUdnia hunodes. 



16 

black type of the disease, Avhich is perhaps the more common, is the 
one referred to in this bulletin unless otherwise stated, as it has been 
possible to study it more thoroughly (PL III, fig. 1). 

The disease having made its appearance in one or more trees ex- 
tends to the surrounding coffee trees. Its advance, which is very 
slow, is marked by the dying or dead coffee trees at the edge of the 
diseased area. In one case, when it was possible to determine the rate 
of progress fairly readily because of the disease attacking the thick 
herl3aceous undergrowth, it covered from 10 to 12 feet in one year. 
Usually the growth is less rapid than in this instance. The only 
things which retard or stop its progress seem to be excessively dry or 
excessively wet soils, natural barriers, such as brooks, and the scarcity 
of food material (decajang vegetation) in the soil. The conditions 
favoring its growth are those provided by moist shaded soils, which 
usually offer an abundance of food material. Unfortunately, these con- 
ditions are also those favorable to the coffee tree, so that the disease 
often does most harm among the best trees, the sun-exposed dry slopes 
of poor coffee plantations remaining quite free from the trouble. In 
more than one instance it has seemed to start with the decay of a 
stump or tree trunk. As the fungus is laiown to live on dead vege- 
table matter, it is probable that these stumps furnish such abundance 
of food material that it becomes strong enough to attack living plants, 
whereas ordinarily it merely makes use of the usual decaying mate- 
rial covering the soil in well-shaded places. 

In the black form of the disease that part of the trunk just above 
the surface of the ground becomes covered for a few inches with a 
thin brown closely adhering coating of the fungus mycelium soon 
after being attacked. On the roots and parts of the trunk below 
the surface the mycelium is gathered more into strands of a brown 
color which later becomes black. Below the thin outer bark the 
threads form a nearly solid layer, thickly grow^n together. From 
this there extends into the bark and wood root-like branches less than 
1 millimeter thick. On cutting away the bark and wood these ap- 
pear as small black dots and lines, according to the angle at which 
they are cut. These form one of the most characteristic features of 
the disease. In trees recently killed the fungus will be found to have 
passed but little deeper than the inner bark, although in old stumps 
it may penetrate 2 or 3 centimeters. The attack is usually near the 
surface of the ground, involving the trunk at the surface and some- 
times also the uppermost roots. It later advances downward for a 
few inches, but the deeper roots usually remain uninjured. Occa- 
sionally on that part of the fungus growth near the base of the trunk 
there are formed numerous small hair-like projections 1 to 3 milli- 
meters long. These are light colored at the tips, close together, and 
have a somewhat brush-like appearance. At first they are evenly 



Bui. 17, Porto Rico Agr. Expt, Station. 



Plate III. 




iT "^ 







Bui. 17, Porto Rico Agr. Expt. Station. 



Plate IV. 




17 

distributed, but later appear in clusters beneath which are formed 
wart-like outgrowths (sclerotia). The hair-like projections bear 
minute spores which doubtless serve to distribute the fungus to some 
extent. (PI. VIII, B.) This stage of the fungus (Dematophora) is 
quite common, though produced less frequently on coffee than on 
many other plants. (PI. Ill, fig. 2.) In the sclerotia are sometimes 
formed other kinds of reproductive bodies that are characteristic of 
the genus Rosellinia. (PI. VIII, A.) This seems quite rare, as the 
writer has found it but twice, once on a wild shrub {Pijyer sp.) and 
once on coffee. 

Among other plants than coffee which this fungus attacks is anamii 
{Petiveria alliacea) , a weed quite common among the coffee. It was 
observed to kill out a thickly growing area of this plant, a grass 
(palmilla) taking its place. No other plant among the coffee has 
been found to be injured except young guamas. Once when the fun- 
gus escaped from pots of infected coffee plants it destroj^ed the 
near-by growing ornamentals, Graftophyllum pictu7n, Panax j)lu- 
rtiatum^ and Acalyph^ Tnosaica. It has been noticed once among the 
trees and low growths at the edge of a clearing, attacking and killing 
nearly all the plants with which it came in contact, among which, be- 
sides the rose apple, were species of Miconia, Piper, and Palicourea, 
all of shrubby habit. A Tradescantia, one of the common ground 
plants in well-shaded coffee, covered the ground as soon as it was 
cleared by the fungus. A fern {Adianfum sp.) seemed to be the 
only plant able to resist its attacks except the large, thick-barked 
guamas and mangoes. The fungus left a vegetation quite different 
from that which it found, causing it to appear somewhat like that 
of the clearings made for coffee. 

Although acting slowly, the losses to coffee produced by root dis- 
eases are probably not exceeded by those from any other cause. The 
injury is greater because the better trees suffer most, especially in 
the case of the black root disease. The fungus causing this disease 
is distributed throughout the coffee-growing regions of the island, 
not being limited by climatic factors as are some other diseases. The 
places where the trees have been killed are often left for a long time 
before replanting, and after the trees are reestablished it is several 
years before they bear fully. Just how long before the ground be- 
comes fit for replanting without treating the soil with some fungicide 
has not yet been determined, but this probably depends on the amount 
of food material available to the fungus in the soil. In one case 
noticed the trees replanted where the vegetation had been killed two 
years previously have not shown, during a period of eighteen months, 
any sign of the disease. 

Some experiments were made with the hope of finding an effective 
way of controlling the disease. These have included ditching about 



Ig 

the diseased areas, a method coiuaionly recommended for this sort 
of disease as a means of preventing the spread of the fungus to un- 
infected areas, and the treatment of the soil with substances having 
some degree of fungicidal action. The ditching seemed especially 
advisable, because the fungus is superficial, never penetrating the 
soil for more than a few inches. The substances added to the soil 
included lime, sulphur, chloronaphtholeum, and copper sulphate. 
These were selected as being fairly easily procured and quite cheap, 
if not too great quantities should be necessary for their effective 
use. Other substances used included potassium permanganate and 
potassium bisulphite. The effect of breaking up the soil by means of 
heavy hoes, a method quite common in cultivating coffee, was also 
tried in some of the check plats and in all of the other plats. Pre- 
viously to this cultivation all diseased trees and stumps and the 
partly decayed vegetable debris common in such places were re- 
moved. For the lime experiment the soil was first broken, after 
which the lime was applied at the rate of 500 grams per square 
meter, being thrown into shallow trenches and immediately covered. 
The trenches being close together and parallel, the application was 
thorough, no part of the surface being overlooked. The ground was 
sprinkled with water to slake the lime and then worked with hoes 
to mix it with the soil. Whenever a diseased tree had been re- 
moved an extra amount of lime was added. Similar methods were 
used in applying the sulphur, care being taken to mix it thoroughly 
with the soil. Two areas were treated, one receiving 500 grams per 
square meter, the other about one-fourth of this amount. The chlo- 
ronaphtholeum, a petroleum distillate product of the same class as 
carbolineum, was used in one of the worst diseased places. It was 
applied at the rate of about 50 cubic centimeters per square meter, 
being poured in 5 per cent solution into small holes which were 
made about a foot apart. Later the ground was sprayed with this 
solution and then worked over with hoes to secure more thorough 
penetration. 

During the three years since the experiment was begun no trees 
have died in plats receiving lime and the heavier application of 
sulphur. In the check plat adjacent to that receiving lime 6 per 
cent of the trees have died, and about 3 per cent of the trees in the 
plat with the smaller application of sulphur and in that receiving 
the chloronaphtholeum. In a plat of anamii showing this disease 
an application of chloronaphtholeum amounting to 100 cubic centi- 
meters of the undiluted preparation and another with the excessive 
amount of 450 cubic centimeters per square meter were made. The 
heavier application stopped the disease without injuring the healthy 
plants. The disease was unchecked by the lighter application, all 
the plants in this plat being killed by the fungus. In any event 



19 

treatment with preparations of this nature is not to be considered, 
as it is ineffective if the smaller quantities are used and its cost 
prohibits the use of large amounts. 

Although the use of lime for this disease promised little, still it 
had the advantage of being very cheap and readily procured be- 
sides being often useful in its effects on the physical condition of 
the soil. Moreover, if it is even of small merit in combating the 
disease it is to be recommended, as, being already familiar to the 
planters, they would use it in preference to other more effective but 
less common materials. The good results obtained from its use in 
these field experiments may be partly due to the disinfecting action 
of the heat of slaking and possibly, also, to lessening the amount 
of vegetable matter in the soil which could be used by the fungus 
as food. That the heat generated by slaking may have had some 
fungicidal effect is further indicated by the fact that when the 
already slaked lime was used in the form of a thin paste at the 
rate of 200 grams per square meter on a much-diseased plat of 
Petiveria no effect in checking the progress of the fungus was to be 
observed. The use of air-slaked lime is not to be recommended in 
the case of the black root disease if it is wished to check the disease 
at once by its application. Its effect will be good only as it tends 
to improve the soil and hasten somewhat the decomposition of the 
vegetable matter on which the fungus feeds. Such action in any 
event will be slow. 

The good results from the use of sulphur must be referred to its 
fungicidal properties. In well-aerated soils sulphur dioxid is prob- 
ably formed, and hydrogen sulphid in soils excessively moist. Both 
of these substances have weak action as disinfectants. But it is not 
unlikely that their continuous production through several months 
would serve at least to prevent the growth of the fungus and perhaps 
to destroy it. Additional evidence that some such action exists was 
obtained by mixing sulphur in the soil with which a trench about 
4 inches deep and of equal width was filled, using about 15 grams 
of sulphur to each meter of the trench. The fungus has killed the 
plants up to the sulphured soil, but during the entire year on which 
it has been observed has not passed to the healthy plants on the other 
side. In part of the ditch which received no sulphur the fungus has 
passed over and destroyed the Petiveria plants. 

In the three years since this work was begun 2 per cent, or 6 out 
of 317, trees have died in the treated plats, all of these being in the 
plats receiving the smaller applications of sulphur and chloronaph- 
tholeum. None have died in those treated with the other disin- 
fectants, but the results from the treatment with these substances 
are of little interest because of their cost. In the check plats which 
were merely cleaned and ditched 5 per cent, or 16 out of 334, trees 



20 

have died. Although it is as yet impossible to arrive at definite con- 
clusions, it would seem that treatment of the soil with some sub- 
stance rendering conditions unfavorable for the growth of the fungus 
was of practical value. 

As to the cost of materials used, that of lime sufficient for 100 
square meters is but 35 cents. The cost of sulphur at the rate used 
in the experiment would be 10 times as much. However, it would 
be worth while to use even such remedies if cheaper materials were 
less successful. If begun while the diseased areas are not too large 
the expense for such treatment would be small. 

As copper sulphate is a substance which is injurious to plant life, 
except in very small quantity, it was not thought desirable to apply it 
so freely to the soil as the other substances used. Accordingly it was 
applied only to the trees near those attacked by Rosellinia. A quan- 
tity equivalent to 15 grams of the salt was sprayed about the base of 
the trees. Within a few weeks the fungus had passed the sprayed 
trees, killing all the Petiveria except near the coffee trees. The form 
of the disease that remains in places where the fungus has passed 
seems to be less virulent, probably because less well nourished. After 
the copper salt has been washed out b}'^ rains the trees so treated will 
probably be subject to attack from the fungus as soon as enough food 
material accumulates to give it sufficient start. The spraying of the 
entire surface with a solution of copper sulphate was tried, the spray 
being of such concentration as to equal 25 grams of the salt per square 
meter. This was found in an experiment on 8 square meters of land 
badly infested with the black-root disease to be sufficient to check and 
apparently to exterminate the fungus, which has not reappeared 
during the year which has passed since the spraying. The cost for 
the copper salt alone used at this rate amounts to 50 cents, at local 
prices, for a quantity sufficient to treat 100 square meters. Where 
the drainage is good, as on the clay hillsides, not enough of the copper 
is retained in the soil to be harmful to vegetation. Under such con- 
ditions and on soil suitably cleaned this is an effective remedy. Pos- 
sibly a considerably smaller quantity of the copper salt would be 
equally effective. However, since satisfactory results can be secured 
by other means, the use of copper salts in controlling the disease is 
not to be recommended. 

The work carried on so far would indicate that cleaning the land, 
ditching, and liming were of value in combating this disease. The 
cleaning includes the taking up and removal of the diseased and dead 
coffee trees. The usual custom of cutting off the tops of such trees 
and leaving the stump to decay is bad. Such material, together with 
piled-up leaves, branches, and other debris, half-decayed vegetable 
matter which serves the fungus as food material, should be gathered 
in the infested places and burned. Large stumps that can not be 



21 

removed should be ditched about, if they occur in the diseased areas 
that are to be treated, as they sometimes seem to harbor the disease. 
The guava and guama, which are frequently killed by borers, leave 
many such stumps, and for this reason these trees are undesirable 
as shade trees. If the ground is to be broken up, which is an ad- 
vantage if lime is to be added, this should be done immediately after 
the cleaning. The ditches should be a foot wide and of somewhat 
greater depth. Care should be taken to examine the bases of the 
trunks of all the trees to be inclosed by ditches in order to make 
sure that no diseased trees have been left inside from which the dis- 
ease can be communicated to the others. Such an examination will 
usually show some of the healthiest looking trees to be affected with 
the disease, often being girdled just below the surface of the soil. 
The length of time that such trees can live and bear fruit, after 
having been girdled, is indicated by the fact that a coffee tree of 
which the bark was removed for a space of 4 inches about the base, 
the wound having been painted with carbolineum to kill any living 
tissue from which growth might set up, lived for 23 months, bearing 
one full and one partial crop. Any tree showing a diseased patch 
near the crown should be removed. Ditching about the diseased 
areas, together with the gathering and destruction of the diseased 
trees and vegetable debris, constitutes the most important step in 
controlling the disease. After the earth has been broken up unslaked 
lime may be applied, as already described, care being taken not to 
place it too close to the trees. If applied in the dry season it should 
be sprinkled with water to slake it after mixing with the soil. It 
is not likely that a quantity of unslaked lime less than that used in 
the experiment (500 grams per square meter) w^ould be effective. 

To summarize, ditching is recommended as preventing the fungus 
from passing from diseased to healthy trees; cleaning up vegetable 
debris and removal of diseased or dead coffee trees and the addition 
of lime or some other substance to the soil are measures of some value 
in combating the fungus. The ditches should be cleaned out from 
time to time and vegetable material prevented from accumulating 
in the places affected with the disease. Such measures are of special 
value where only a few diseased trees are found among otherwise 
healthy plantings. Where the centers of infection are too numerous 
it may be useless to protect with ditches and even less so to use the 
other sanitary measures mentioned above except, perhaps, the re- 
moval and destruction of diseased trees as soon as observed. 

BERBY SPOT (Cercospora coffeicola). 

This spot of the berry is troublesome since it causes the fleshy 
part of the fruit to adhere to the parchment, thus making the process 
of preparation more difficult. It is also the cause, at least indirectly, 



22 

of part of the injury to the grain which results in its being classed 
as of lower grade. 

The fungus causing this spot, C ercofifora coifeicola, has been re- 
ported from Central and South America. Doubtless it occurs 
throughout the American coffee-growing regions. In Porto Rico it 
is present to some extent in every plantation. Both leaves and berries 
are affected by the disease. On the leaves it causes round spots, 
varying from 6 to 10 millimeters in diameter, of a brownish color 
somewhat lighter toward the center than at the edge. There are 
rarely many on any one leaf, and so little harm is done by the fungus 
as a leaf parasite as to be negligible. On the leaves, however, they 
produce spores which serve to spread the disease and to carry the 
fungus over from one crop to another. On the berries the largest 
spots, those fastening the fleshy part of the fruit to the parchment, 
almost always are found on the upper side. Any part of the fruit 
may be attacked, the spots appearing at first as small brown dis- 
colorations. They are especially common on the nearly ripe berries. 
At the time of picking, the larger spots cover about half of the fruit 
and are velvety with the spore-bearing outgrowths of the fungus. 

The occurrence of the largest and worst spots on the upper or sun- 
exposed side of the berries is to be explained by the fact that the spots 
develop more rapidly in the somewhat riper tissue of that side, such 
uneven ripening of the berry being caused by the direct exposure 
each day to the sun rays. After the berries have become infected 
this one-sided ripening takes place more rapidly, the berries being 
black above with the Cercospora spot and still green on the underside. 
Wliether picked at once or left until thoroughly ripe the berry is 
difficult of preparation and yields a somewhat inferior product. 
That the riper tissue furnishes more favorable conditions for the 
fungus is indicated by the more rapid development of the spots pro- 
duced by inoculation into ripe berries, and the greater number of 
spots developing on the nearly ripe tissue. 

The uniformity with which the upper side of the berries is the part 
most injured may account for the idea that such berries are injured 
by hail. As a matter of fact hail is almost unknown at the eleva- 
tions where the worst affected plantations are situated. Another and 
better explanation quite commonly given is that the berries are 
burned by sun either directly or intensified by the lens-like action of 
drops of water, the disease itself being for this reason sometimes re- 
ferred to as the " sancocho " of the berries. The presence of an or- 
ganism, of proved parasitism, even in the earliest stages of the dis- 
eased spots, makes these theories untenable. Sunlight is a factor of 
importance, but only as it influences the development of the spots that 
happen to occur on the upper side of the berries. These become con- 
spicuous and are thought to be the only ones, the others remaining 



23 

unnoticed. There is, however, a small amount of injury to fruits 
and leaves, not due to parasites, which is to be ascribed to the heat 
of the sun. On the leaves of unshaded coifee trees such injury is 
represented by brown shriveled or sunken patches of cells, which in 
their earliest stages are free from micro-organisms. Occasionally 
such patches of injured cells form the center of yellowish areas. A 
similar loss of chlorophyll on the upper side of the berries precedes 
a premature ripening of the sun-exposed fruit. The berries that 
ripen thus without being attacked by Cercospora are few in number. 
That the injury in the case of the leaves is sun produced is indi- 
cated by the absence of such " burned " tissue in the leaves of shaded 
trees and the fact that those leaves with more nearly horizontal 
or exposed positions are the ones affected. The injury by sunlight 
is of interest in this connection as it favors infection of the fruits by 
Cercospora. 

Since the existence of a close relationship between the distribution 
of the disease and conditions as to shade would make possible a prac- 
tical means of control, it was thought worth while to secure data 
with regard to this. Accordingly samples were taken from each of 
the gatherings made in two fields, one with fairly heavy shade, the 
other exposed to the full sunlight. The quantity of berries examined 
from each field varied from 132 to 199 liters per season, amounting to 
from 15 to 20 per cent of the entire yield. The conditions as to soil 
and slope were fairly uniform in each, so that the samples may be 
taken as representing the quality of output fairly well. For two 
years determinations were made of the proportion of Cercospora- 
spotted berries, including spots of 1 millimeter in length or more. 
It was found to vary according to the degree of maturity of the 
samples examined, but reached for the last year 73 per cent for the 
shaded and 70 per cent of such berries for the sun exposed. It was 
concluded that, so far as the actual distribution of the disease goes, it 
is not influenced largely by differences with regard to light. The 
relative occurrence of the more troublesome or " sancocho " form of 
the spots was quite different as, in the determinations made the fol- 
lowing year, when there were taken only berries in which the spots 
were sufficiently developed to be blackened and dried to the cascara, 
it was found to be 16 per cent in the shaded and 27 in the unshaded 
coffee. 

It is well known that there is considerable variation in the quality 
of coffee, one of the characters of an inferior grade being the larger 
proportion of blackened and shriveled grains. As it was thought the 
Cercospora spot of the berry might be the cause of such grains, at 
least indirectly, the spotted berries, used in the work already men- 
tioned, were subjected to the usual process of preparing the grain. 
In the case of those used in the earlier work, where even slightly 



24 

spotted berries were included, only those of which the parchment was 
found, in the course of preparation, to be injured or seriously dis- 
colored were selected for the final preparation, such parchment being 
taken as corresponding to the larger, deeper Cercospora spots. 
Those with sound parchment were not considered farther except to 
be measured, as it was thought that sound berries or those slightly 
spotted would give only good grains. Later it was' found that some 
of the injury to the parchment on the berries selected for final prepa- 
ration was due to merely mechanical injury of the pulping machine. 
Moreover, it was found that a certain proportion of the sound berries 
contained bad grains. The results are for this reason not given in 
full, although they give as uniform and pronounced differences in 
favor of the product of the shaded trees as the later, more accurate 
work. Of the grains with any sort of injury the percentage was 33 
for the unshaded trees and 19 for the shaded the first year, and the 
following year 29 and 20 per cent, respectively. 

During the last season in which this work was carried on only the 
more severely attacked berries or those in which some effect on the 
grain seemed possible were used, the slightly affected ones being 
classed with the sound berries. The proportion of imperfect grains 
of all sorts was determined, and of these the blackened ones were 
separated and also determined. The results given in percentages are 

as follows: 

The effect of shade on the quality of the grain. 



Shaded. 



Un- 
shaded. 



All injured grains in good berries 

Blackened grains in good berries 

All injured grains in badly spotted berries. 
Blackened grains in badly spotted berries. 



Per cent. 

4.5 

2.0 

27.0 

9.0 



Per cent. 
19.0 
11.0 
45.0 
36.0 



It is evident that the berries more severely spotted by Cercospora 
contain a greater proportion of bad grains than the unspotted, indi- 
cating that the fungus does influence the quality of the grain unfavor- 
ably. That the sound- appearing berries should give so much inferior 
grain or any at all is surprising and not yet well understood. The 
larger proportion of bad grains in the Cercospora-affected berries 
from the imshaded field is in accordance with the greater abundance 
of the more severely attacked berries generally apparent in such con- 
ditions. The results show in every instance, whether from spotted 
or sound berries, a smaller proportion of bad grains to be produced 
from the shaded field. 

It is clear that Cercospora has nothing to do with a considerable 
proportion of the inferior grains, since they occur in sound berries. It 
has never been found among the organisms isolated from the grains 



Bui. 17, Porto Rico Agr. Expt. Station. 



Plate V. 




Trunk of Coffee Tree with Fusarium Disease Produced by Inoculation. 



j|. 17, Porto Rico Agr. Expt. Station. 



Plate VI. 




Root of Coffee Tree. Roughened Bark Due to Nematodes. Roots Killed by 
"White" Root Fungus. 



Bui. 17, Porto Rico Agr. Expt. Station. 



Plate VII. 





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Bui. 17, Porto Rico Agr. Expt. Station. 



Plate VIII. 




A.— AscusAND Spores OF Roselliniasp. (x450). B.-Hyph/eand Spores of Deivia- 

TOPHORA SP. 1X450). C— HYPH/E AND SPORES OF CEPHALOSPORIUM SP. (X450). 



25 

of these berries nor from those of the spotted berries. Such in- 
jurious effect as it may have on the grain must be due to the shrink- 
age resulting from increased loss of water from the spotted fruits, as 
well as the admittance through the weakened tissue, at the point 
attacked, of other organisms which attack the grain directly. Of 
these several haA^e so far been found, the most common being a 
Fusarium, identical, apparently, with this stage of the Sphserostilbe, 
already mentioned. The injury resulting from the spot seems to 
depend on the age of the fruit attacked. When the infection takes 
place on undeveloped fruits the resulting injury is greater, but if 
the grain has begun to harden before the spot develops fully it may 
escape injury. 

Another source of the inferior quality of coffee from sun-exposed 
fields is to be found in the " granos vanos," berries that seem to be 
well filled out and good, but which are easily recognized at the time of 
picking by their yielding readily to the pressure of the hand and also 
by the dried, blackened pedicels. The name could be applied as well to 
the sound-appearing berries with bad grains mentioned above, but for 
convenience it is here used to indicate those the injury to which is due 
to the supply of food material having been cut off, as shown by the 
dead pedicels. Not isolated berries alone, but often all on one branch 
or the entire tree are affected in this way. The shriveled grain con- 
tained in these berries remains free from fungi or bacteria for a long 
time, the injury being clearly not due to these organisms. The black- 
ened tissue of the branch at the base of the pedicels always contains a 
Glcesporium, and occasionally a Fusarium. But neither of these 
fungi was found to be able to attack the tissue of healthy green 
branches when tried out by inoculations with pure cultures. It would 
seem that they are only able to attack weakened trees exposed to full 
sunlight and subject to the unfavorable soil conditions accompanying 
such exposure. Not all the trees in unfavorable conditions produced 
berries of this sort. What the proportion may be was not determined, 
but it is only large in the first picking. This was omitted in the 
earlier work, and in that of the last year the " gi-anos vanos " were 
separated out, so that the result can not be affected to any extent by 
their presence in the samples. The hormiguilla {M yrmelachista sp.) 
is to some extent the cause of these " empty berries," as it often injures 
the base of the fruit-bearing branches and sometimes the pedicels, 
thus cutting off' their supply of food. 

It is known that the soil in well-shaded places is more uniformly 
moist than in more exposed situations, and no doubt the benefit of 
shade in coffee is in part due to better soil conditions, especially with 
regard to moisture. The soil in unshaded places becomes very dry in 
the season of little rains and also very hard where of the clay type. 
The unfavorable condition as to moisture is made worse by the pres- 



26 

ence of grasses which always come in where shade is lacking. The 
trees in these places are slender, with few branches and but little 
foliage. The leaves of the branches on which berries set fall when 
these are half grown and the branches begin to die back at the tips. 
Where the blackening extends rapidly, killing the bark and pedicels, 
the " granos vanos " result. The trees, which are dependent on new 
branches for leaves and berries, are able to form but few of these. 
A product of inferior quality results, owing to the action of certain 
diseases of the fruits and grain, thus increasing the loss caused by 
lessened yield. 

STUDIES OF THE SPOT FUNGTJS. 

It is desired to include at this place something of the technical part 
of the study. In attempting to determine definitely the nature of 
the organism producing the spots, the earliest stages of the spots 
were studied. The berries with such spots were first sterilized and 
then introduced into the medium, or the spot itself was cut out and 
introduced into the medium, using the usual precautions. When the 
sterilization had consisted in washing the berries for three minutes 
in 90 per cent alcohol, then placing them in 4 per cent formalin for 
three minutes, and finally w^ashing in sterilized water, the spotted 
berries usually gave, in addition to a sterile gray fungus, a Gloeo- 
sporium, while the check unspotted berries similarly sterilized often 
gave a Gloeosporium. With less severe sterilization a Fusarium Avas 
often obtained in addition to the above. Later work, with more 
thorough sterilization, gave only the sterile fungus from the spots. 
Both the Fusarium and the Gloeosporium were tested in inoculations, 
but without positive results. The sterile fungus was used in inocu- 
lations, with the results that typical spots were produced on which 
Cercospora spores later developed. In the checks small pieces of 
sterile absorbent cotton of about the same size as the pieces of 
mycelium were introduced into small wounds, the purpose being 
roughly to duplicate the conditions of the inoculation. No infection 
resulted in the case of those checks, although the chances of such 
mfection from natural sources existed. No attempt to sterilize the 
berries on the trees before this inoculation was made, and the results 
showed it to be unnecessary. From the spots resulting from the 
inoculation the usual gray sterile fungus was reisolated. 

No spores of Cercospora were borne on the mycelium in artificial 
culture. However, on some of the mycelium placed on the berries 
but slightly introduced into the wound, abundant spores of Cerco- 
spora were in one instance produced. The material used in the inocu- 
lations of the following season was obtained from spores developing 
on typical spots of the berries. The spores, because of their com- 
paratively large size, are easily isolated from drop cultures. The 



27 

germinating spores were transferred directly from the agar of these 
cultures to the usual media. In every case the typical gray sterile 
mycelium, similar in every way to that used in the inoculations of 
the preceding year, resulted. This when inoculated into the berries 
produced the usual spots from which it was reisolated, and there can 
thus be no doubt as to the identit}^ of the organism producing this 
spot. An attempt was made to show that the spot on the berry could 
be produced by spores from the leaf spots. When transferred di- 
rectly from the leaves to the berries no infection resulted. Later 
pure cultures from the spores of the Cercospora of the leaf were 
obtained, as in the case of that of the berry. The resulting growth, 
which was similar in every way to that in cultures of the berry 
fungus, when inoculated into the berries, gave positive results, typi- 
cal Cercospora spores later developing. 

In conclusion it may be said that the spot of the berries produced 
by Cercospora coffeicola^ which besides interfering with the prepa- 
ration by causing the flesh to dry and adhere to the berry also injures 
the grain to some extent, may be largely prevented by the use of suffi- 
cient shade, as, for example, that of sufficient density to prevent the 
growth of grasses other than palmilla. Such shade is distinctly 
favorable to the production of coffee free from inferior shrunken 
grains. 

MISCELLANEOUS DISEASES. 

Of less importance but perhaps worth mentioning in any general 
discussion of coffee diseases are the " zoned " leaf spot and a root 
and trunk disease. The leaf spot is characterized by its tendency 
to develop concentric rings, such rings being sometimes incomplete 
at the outside of the spot, and often beginning as entirely separate 
spots which increase until united with the central mass (PI. IV). 
On the underside of the older spots a thin white mold appears after 
a while, which is condensed or massed in places. This bears the 
numerous spores of the fungus {C&phalosporium sp.) (PI. VIII, C.) 
which has been shown to be the cause of the spot by isolation from 
the beginning spots and by inoculations from pure culture. The 
disease is common among the best coffee, seeming to prefer the young 
and well-shaded leaves, and all the various species and varieties 
cultivated at this station are subject to attack, though it is most 
common on the "Ceylon Hybrid." It has been noticed on other 
plantations but is nowhere abundant. 

Another disease is easily recognized by the smaller diameter of 
the affected part of the trunk owing to the bark drying up and 
shrinking (PL V). After being diseased for a long time the bark 
falls away leaving the wood exposed and the calloused outgrowths 
at the edge of the healthy bark. If the diseased bark is cut away 



28 

the wood will be found to be blackened as if somewhat charred. A 
fungus, Fusarium sp., is always present in the diseased tissue, but 
inoculations with pure cultures have failed to produce the disease. 
It is communicated readily to healthy trunks by means of small 
pieces of diseased material, and when thus transferred has shown 
itself to be rapidly developing and destructive, soon killing the 
living tissue for several inches above and below the point of inocu- 
lation. 

Infection appears to take place through wounds, as, for example, 
the stumps left by cutting off part of the branches close to the ground. 
It frequently accompanies the " white " root disease, attacking the 
yet living trunk above the diseased roots. It seems probable that it 
can attack the tree near the crown through small wounds such as 
those made by the machete in weeding, but no clear evidence of this 
has been found. The characteristic Fusarium was isolated from a 
decorticating disease of coffee where all the trees were attacked -at 
some 2 or 3 feet from the ground. In this case ants and mealy bugs 
were also present, so that the injury was probably due in the first 
place to these insects. The decorticated branches with the enlarged 
outgrowths of healthy tissue at the base of the branches occasionally 
to be seen are no doubt the after effects of this form of the trunk 
disease. 

The foregoing includes all the commoner and more destructive 
Porto Rican coffee diseases produced by fungi. One disease, that 
caused by Hemileia vastatHx^ which is said to have caused so much 
damage to the cultivation of this plant in India and the East Indies, 
does not occur here and has not been reported from any American 
coffee-growing country. The threadworm Heterodera radicicola^ is 
often active in trees suffering from root disease, being found in such 
cases at the upper edge of the diseased area at the base of the trunk 
(PL VI). It was thought at first that it might be the real cause of 
the white-root disease, but since specimens have been found free from 
this worm there can be no necessary relation between the two. It 
attacks the bases of the trunk, however, causing them to take on a 
roughened, somewhat swollen appearance for a foot or so above the 
soil. When cut into with a knife there may be seen, even with the 
naked eye, the minute globular bodies of the adult females, by which 
such diseased tissue is characterized. No real evidence that the trees 
are really injured by this disease has been noticed. The character- 
istic swellings caused on roots by this worm may sometimes be seen 
on the fine roots near the surface. The heavy nature of most Porto 
Rican coffee soils no doubt prevents it from becoming the pest which 
it sometimes is elsewhere. 



29 



SUMMARY. 



(1) For leaf rot {Pellicularia holeroga) there has been found no 
really satisfactory method of control. The benefit of repeated spray- 
ings with Bordeaux mixture is lessened by the fact that the fungus 
is not all killed even by repeated sprayings, enough remaining to 
reinfect the trees after a time. 

(2) For leaf spot {Stilhella jiavida) Bordeaux mixture is really 
effective, and it may be recommended to prevent the disease from 
extending to healthy and productive plantings. 

(3) Cercospora spot of the berries, which causes the more badly 
affected berries to be pulped with difficulty, and also injures the 
grain to some extent, is to be prevented in its worst form by provid- 
ing sufficient shade, which by rendering less harmful this and other 
sources of injury to the grain decidedly improves the quality of the 
output. 

(4) The root disease may be prevented from spreading by ditch- 
ing, this being preceded by the removal and destruction of vegetable 
debris, diseased trees, and stumps. It is apparent that the addition 
of unslaked lime, sulphur, and some other substances to the soil 
prevents the growth of the fimgus causing the disease. 

(5) Importance is to be placed on the use of preventive measures 
to keep the stiU healthy younger plantings in good condition rather 
than on attempts to exterminate the diseases among the older trees. 



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